I wouldn't buy a full shroud GP100 or a 686/686P... they have those full length shrouds/lugs, which I don't like. I bought new a 2" 10 and a 6" 66 (With 'Lock'!) as my first .38 & .357M's 9/03. I made some .38's and .38-level .357M's for them - before they arrived. I also bought a HiVis front sight and Ahrends square conversion f.g. cocobolo stocks for the 66, installing same when they arrived. I fired my first ever .38's and .357M's, albeit mild ones, the next day - wow! The only commercial ammo either has seen is the Rem 'FBI' load, 158gr LHPSWC +P's.
Skip ahead... S&W produces a 'Stocking Dealer Exclusive' - a 5" HALF LUG 686+... with the same Ahrends and HiViz, not to mention a V-notch rear... and marked $30 less than a regular 4" 686 - go figure! I did some horse-trading, and brought it home. Despite it's similarities to that 6" 66, it is different. I like them both, but the 686+ will be here long after my old friend 66 goes. It feels fine... actually, balances/points as well as the 6" 66. Sadly, I have since shot the range's rental 4" 686+... even with the dreaded OEM Hogue's, it was quite good. I feel that even with .357M's, a set of Ahrend's cocobolo square conversion stocks will be sufficient - and feel and look great! And, the Uncle Mike's Combats, rounded or squared, as delivered on the K-frames, cover the backstrap for a better feel, at least to me, than those OEM's - and, they are still available from S&W Accessories. The HKS 587 7-shooter speedloader works fine with either grip - and a couple of them should be your first purchase.
Yeah, as someone told me - after finally getting my 5" h-l 686+ - you don't 'see' that full lug when you are shooting. You'll enjoy that 686+, believe me.
Stainz
PS I had one nagging problem... difficulty shutting the cylinder earlier this year. I traced it down to a piece of brass wire, from a bore or chamber brush, wrapped in the crotch between the ejector star and around the rod. So little, yet so important... gotta wear my reading glasses when I clean!